About your space colony, Dr. Hawking...

07 Dec 2006

Is it time to abandon Earth?

Stephen Hawking has been saying for the past few years that humans should colonize space. Another story came out last week after he was awarded the Copley medal -- flown in space by NASA for his benefit -- so it is a timely story:

"Sooner or later disasters such as an asteroid collision or a nuclear war could wipe us all out," said Professor Hawking, who was crippled by a muscle disease at the age of 21 and who speaks through a computerized voice synthesizer.

"But once we spread out into space and establish independent colonies, our future should be safe," said Hawking, who was due to receive the world's oldest award for scientific achievement, the Copley medal, from Britain's Royal Society on Thursday.

"I don't think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I'm an optimist. We will reach out to the stars."

I can understand the sentiment. Certainly, a nearby supernova could easily blast through our solar system, taking us with it. Hawking has gone a bit far in his worrying -- in recent talks he has been stressing dangers like global warming, which -- although probably very inconvenient and costly -- is almost certainly not going to wipe us out. I think we stand a pretty good chance of surviving most meteor hits, and a bit of preventative space medicine might be enough to avoid them entirely. Yes, in a few billion years the sun is going to envelop us when it goes red giant, but a few billion years is a long time.

I guess for me, the important aspects of the question are all anthropological. Is space colonization going to fix anything, or is it going to make matters worse? I don't accept the space boosters' position, because we hear so little about the downsides of space colonization. There is a good argument that colonizing space will make things worse for most of humanity.

It takes incredibly high energies to propel people through space. The higher the velocity, the higher the energies. Get up to a reasonable fraction of light speed, and it begins to take more power than the entire power produced by all sources on Earth, at least currently.

Now, we can imagine that technology will improve, that Earth may produce more energy, or that we will harnass energy from some other astronomical source. But the fact remains that we have a tradeoff -- we can accelerate a few people very fast, or a lot of people very slowly.

Nobody is suggesting that we will ever have the transport potential to evacuate the Earth completely. By midcentury we will be looking at a global population of 10 billion people. If we colonized Mars with only 10,000 people it would be a major accomplishment, costing trillions of dollars. If we send 10,000 people to another star system along with a millenia-enduring habitat and seed DNA and facilities to terraform a distant planet, it would be enormous -- an investment far greater than the current energy and wealth production of the Earth.

It is unquestionably true that successful space colonies would allow humanity to survive the destruction of the Earth. Indeed, a colony sent to a distant star system might -- if it succeeded -- ultimately proliferate to numbers comparable to the Earth's population.

But the people on Earth who would pay for these ventures derive little direct benefit from them.

Consider: a colony of 10,000 people fly to a distant star, a journey that takes them several hundred years. The distant descendants of those people will spend thousands of years terraforming a planet. The colony that they establish may be in relatively constant communication with Earth, although with a several decade delay, so we might learn much about this distant planet and the travails of space colonization.
But these people, at the time that they leave, are only a tiny fraction of humanity -- around 1 in a million people. How will we choose them? Do we take whoever wants to go?

Should we choose the most genetically variable sample of people? There is a rationale for this -- they will have the most alleles to deal with new environmental challenges. Also, they will be more representative, on average, of the genetic variation of people on Earth.

Or maybe we should choose people who have genes suited for long spaceflight. Maybe people who are unlikely to suffer from claustrophobia, or who can deal with the cardiovascular risks that come from a special long-term exercise regimen. Maybe they need to be people who get the most energy out of the limited number of food species that can be grown in their space habitat.

The point is, that whoever we choose, they will have a miniscule genetic relationship to most of the people on Earth. These are not our children; they are somebody else's children. They have a chance of immense genetic success when they reach their destination. They certainly bear a risk -- their ship might explode, or any number of other things. But the capital costs of their mission will be paid by our children and grandchildren, possibly for many generations. Why should our great-great grandchildren live in the world diminished by the exodus of a lucky few?

There is certainly no direct benefit to people left behind in the event that the Earth really is destroyed! Sure, a few Earthlings will have scattered elsewhere, but that is cold comfort to those who face the asteroid impact. We would be better off spending the money to destroy or deflect near-Earth asteroids!

In other words, the "don't put all your eggs in one basket" argument makes a very unrealistic assumption. The question here is whether it is better to (a) put all but one of your eggs in one flimsy basket and put one egg in one incredibly expensive Kevlar basket, or whether it might be better to (b) use the same money to reinforce the one flimsy basket.

If the choice is still difficult, try to remember that you and your children are in the flimsy basket, no matter what!

I can't imagine a situation where it is better to make my grandchildren pay for a hugely expensive space mission than it would be for them to pay for a hugely expensive overhaul for Earth's energy supplies, or a hugely expensive asteroid deflector system, or any number of other things to protect the 10 billion people at home. Sure, there are some risks that we can probably not prevent, like a supernova shock wave. But these are risks that we can't escape by colonizing nearby star systems. They will get hit by the supernova, too!

Establishing colonies on the Moon or Mars is much less expensive, and people on Earth might actually get to go there sometime during their lives. A Martian colony might send resources back to Earth, and people might choose to travel there to help build it. Or maybe they want to spend their retirement in lower gravity that hurts their joints less. Maybe terraforming Mars will give us scientific knowledge to help control our own climate.

But whatever comes from these efforts, it is hard to imagine that the same amount of money wouldn't be better invested here on Earth. Remember that a single mission to Mars by a small group of astronauts is likely to cost upwards of 40 billion dollars. I don't see global warming as a threat to humanity. But even supposing that it could wipe us all off the map, 40 billion dollars spent to research it would be far better spent than 40 billion dollars spent on a Mars trip. "Better spent" because the people paying the 40 billion dollars -- our children and grandchildren, again -- will be far more likely to benefit from the increased knowledge of global warming, than they are to benefit from shipping 5 people to Mars for a few weeks.

It seems ludicrous to spend a few trillion on a serious Mars colony, when the same few trillion might combat global warming, establish a series of asteroid deflectors, and find an effective means of harnassing fusion energy. Especially since the few thousand people in that Mars colony will be incapable of surviving themselves over the long term if Earth was suddenly destroyed. Even terraforming is at best marginal in its ability to make Mars habitable over the long term.

And remember the genetic interest argument. Suppose people sent to another star system get there, establish their colony, and start to succeed. They have an increasingly tiny genetic relationship to our own descendants here on Earth. They will see on Earth's television signals how many people are interested in making the journey to their new paradise, taking up resources from their own descendants.

How long will it take them to realize that they have all the equipment to come back to Earth, wipe humans out, and terraform it to their own liking?

John Hawks is the Vilas-Borghesi Distinguished Achievement Professor of Anthropology at the University of Wisconsin—Madison. I work on the fossil and genetic record of human evolution (About me).

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